Physical workload of flight attendants when pushing and pulling trolleys aboard aircraft

Int Arch Occup Environ Health

Gawliczek

et al. 2014

ObjectivesAs knee-straining postures such as kneeling and squatting are known to be risk factors for knee disorders, there is a need for effective exposure assessment at the workplace. Therefore, the aim of this study was to develop a method to capture knee-straining postures for entire work shifts by combining measurement techniques with the information obtained from diaries, and thus avoiding measuring entire work shifts. This approach was applied to various occupational tasks to obtain an overview of typical exposure values in current specific occupations.MethodsThe analyses were carried out in the field using an ambulatory measuring system (CUELA) to assess posture combined with one-day self-reported occupational diaries describing the durations of various work tasks. In total, 242 work shifts were measured, representing 81 typical tasks from 16 professions. Knee-straining postures were analysed as daily time intervals for five different postures. The accuracy of the method was examined by comparing the results to measurements of entire work shifts.ResultsUnsupported kneeling was the most widely used knee posture in our sample (median 11.4 % per work shift), followed by supported kneeling (3.0 %), sitting on heels (1.1 %), squatting (0.7 %), and crawling (0.0 %). The daily time spent in knee-straining postures varied considerably, both between the individual occupations, within an occupation (e.g. parquet layers: 0.0–88.9 %), and to some extent even within a single task (e.g. preparation work of floor layers (22.0 ± 23.0 %). The applied measuring method for obtaining daily exposure to the knee has been proven valid and efficient randomly compared with whole-shift measurements (p = 0.27).ConclusionsThe daily degree of postural exposure to the knee showed a huge variation within the analysed job categories and seemed to be dependent on the particular tasks performed. The results of this study may help to develop an exposure matrix with respect to occupational knee-straining postures. The tested combination of task-based measurement and diary information may be a promising option for providing a cost-effective assessment tool.

Section: Methodsmentioning

confidence: 99%

Occupational kneeling and squatting: development and validation of an assessment method combining measurements and diaries

Ditchen

Int Arch Occup Environ Health

Gawliczek

et al. 2014

“…Posture capturing was performed between October 2006 and June 2009 directly at the workplaces with the proprietary-developed measuring system CUELA (Ellegast and Kupfer 2000; Freitag et al 2007; Glitsch et al 2007). The mechanical-electronic system consists of gyroscopes, inclinometers, and potentiometers that can be fixed on a subject’s clothes with a belt system.…”

Section: Methodsmentioning

confidence: 99%

Validity of self-reports of knee-straining activities at work: a field study with 6-month follow-up

Ditchen

Int Arch Occup Environ Health

Hartmann³

2012

ObjectivesTo measure short-term and long-term validity of self-reported duration of kneeling and squatting at work and to examine the possibility of differential misclassification due to knee complaints.MethodsWork-related kneeling and squatting were analysed for 190 male subjects (mean age, 35.0 and SD, 11.5) in field by both measurements and questionnaires. Posture capturing was performed with an ambulatory measuring system (CUELA). Immediately after the measurement (t0), each participant was asked to estimate frequency and duration of five specific knee postures taken during the measurement period. After 6 months (t1), the survey was repeated (n = 125). Health status of all subjects was recorded by Nordic questionnaire. Statistical analysis was performed by using nonparametric tests, correlations, and Bland–Altman plots.ResultsAt both time points, subjects were able to recall the occurrence of knee postures rather well (100.0–57.6 % agreement) but many of them failed in quantifying their knee load. We found poor-to-moderate correlations between measurements and self-reports for all examined postures in both surveys (0.23 < ρ < 0.63). The durations of knee postures were both over- and underestimated but overestimations predominated (t0, 74.7 % and t1, 87.2 % overestimations). High-exposed subjects seemed to misjudge their exposure to a greater extent than low-exposed ones, while knee complaints seemed to have no impact on the assessment behaviour.ConclusionsAs our study showed, self-reported knee loading may deviate widely from measured exposure. These limitations of self-reporting emphasise the arguments in favour of using objective data whenever possible, for example by complementing self-reported occurrence of knee postures with quantitative measurement data.Electronic supplementary materialThe online version of this article (doi:10.1007/s00420-012-0758-4) contains supplementary material, which is available to authorized users.

“…<7;,backward) that: were combined using the Slerp function qt = S l e t p (<7r,forward i *7/,backward! ^r) ) 0 5c ^ 1 ( 1 2 ) s, = , Tj € ZPs, Ti < t < Ti+l (13) t ;+i -7/…”

Section: Bidirectional Orientation Estimationmentioning

confidence: 99%

“…How ever, in real workplace environments, it is not possible to avoid magnetic disturbances for long periods of time (e.g., handling of vehicles, machines or tools). The combination of IMUs and me chanical sensors (potentiometer) proved to be reliable in real workplaces [12][13][14], but despite the advantages of such systems, there are still scenarios where sensor technology without mechani cal components would be advantageous.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Inertial Sensor-Based Motion Capturing for Magnetically Distorted Field Applications

Schiefer

Journal of Biomechanical Engineering

Hermanns

et al. 2014

Inertial measurement units (IMU) are gaining increasing importance for human motion tracking in a large variety of applications. IMUs consist of gyroscopes, accelerometers, and magnetometers which provide angular rate, acceleration, and magnetic field information, respectively. In scenarios with a permanently distorted magnetic field, orientation estimation algorithms revert to using only angular rate and acceleration information. The result is an increasing drift error of the heading information. This article describes a method to compensate the orientation drift of IMUs using angular rate and acceleration readings in a quaternion-based algorithm. Zero points (ZP) were introduced, which provide additional heading and gyroscope bias information and were combined with bidirectional orientation computation. The necessary frequency of ZPs to achieve an acceptable error level is derived in this article. In a laboratory environment the method and the effect of varying interval length between ZPs was evaluated. Eight subjects were equipped with seven IMUs at trunk, head and upper extremities. They performed a predefined course of box handling for 40 min at different motion speeds and ranges of motion. The orientation estimation was compared to an optical motion tracking system. The resulting mean root mean squared error (RMSE) of all measurements ranged from 1.7 deg to 7.6 deg (roll and pitch) and from 3.5 deg to 15.0 deg (heading) depending on the measured segment, at a mean interval-length of 1.1 min between two ZPs without magnetometer usage. The 95% limits of agreement (LOA) ranged in best case from -2.9 deg to 3.6 deg at the hip roll angle and in worst case from -19.3 deg to 18.9 deg at the forearm heading angle. This study demonstrates that combining ZPs and bidirectional computation can reduce orientation error of IMUs in environments with magnetic field distortion.